The invention relates to a well packer assembly and more specifically to a straddle packer assembly which has a fluid bypass in the upper packer apparatus to allow reverse circulation of stimulation fluid through the upper packer apparatus.
It is well known to use packers to sealingly engage the casing in a wellbore for a variety of different reasons. Packers are utilized for treating, fracturing, producing, injecting and for other purposes and typically can be set by applying tension or compression to the work string on which a packer is carried. Inflation-type packers which utilize packer elements that are inflatable with an inflation fluid are also commonly used. Packers are often utilized to isolate a section of wellbore which may be either above or below the packer.
Straddle packer assemblies which comprise upper and lower packer apparatus to engage and seal against a casing, or wellbore, are used to isolate a formation therebetween for stimulation or other treatment. Inflation-type straddle packers are well known. There are also straddle packers that include a compression packer and a cup packer, and straddle packers where both the upper and lower packer apparatus comprise compression, tension or hydraulic set type packers. In many cases, it is difficult to move the straddle packer assembly in the well after the stimulation process, in part due to the existence of proppant in the well annulus between the packers. There is currently no known method for reversing sand or other proppant used in a fracturing fluid from the straddle between the two packers in a two-packer compression, tension or hydraulic set system, while the packers are set. Thus, there is a need for a straddle packer apparatus using compression, tension and hydraulic set type packers which will provide for reliable retrievability and movability in a well, and which will provide for the circulation of sand or other proppant from between the straddle when both the upper and lower packers are set.